This invention relates to the removal of tissue from the body such as for example removal of cataracts from the eye.
It is known to remove diseased tissue from the body by fragmenting, crushing or otherwise making the tissue flowable while in the body and then aspirating it. In one known class of surgical techniques of this type specifically intended for the removal of cataracts: (1) an incision is made along the superior corneal margin from about 10 to 2 o'clock (12 o'clock is the location closest to the top of the head of the patient) approximately 10 mm in chord length; (2) an incision is made in the capsular wall; and (3) the cataract is removed. The anterior chamber is maintained substantially formed during the operation by means of a continuous inflow of irrigating solution.
In one prior art technique of this class for removing a cataract, the nucleus is expressed out of the eye and the cortex is removed by a process of irrigation and aspiration. In another prior art technique of this class for removing the cataract, the nucleus is removed with a vectis and about 0.1 milliliter of viscoelastic compound or irrigating fluid is introduced into the capsular bag to separate the capsular walls. With the capsular walls separated, a wedge of the cortex is engaged in the aspiration port of a cannula and peeled toward the center and then aspirated to remove it. This process is repeated so that the layers of the cortex are peeled and then aspirated inwardly through the cannula, layer by layer, until the intact capsular bag (except for the horizontal incision) is completely empty and clean.
This technique of removing the cataract is disclosed by Anis, Aziz Y., "Illustrated Step-by-Step Description of the Anis Dry Extra Capsular Cataract Extraction Technique With In-the-Bag Lens Implementation"; Seminars in Opthalmology, v. 1, N. 2 (June), 1986, pp. 113-129 and the technique is compared with other such techniques of this class.
Two prior art types of instruments which aid in the fragmentation and aspiration of the lens nucleus to permit extraction through a small incision are disclosed in U.S. Pat. No. 3,589,363 to Anton Banko et al.; U.S. Pat. No. 3,902,495 to Steven N. Weiss; U.S. Pat. No. 3,693,612 to Charles Kelman et al.; and U.S. Pat. No. 4,041,947 to Steven N. Weiss et al. This instrument is intended in the prior art to fragment a lens nucleus using ultrasonic vibrations to aid the irrigation/aspiration of the lens. The ultrasonic vibrations laterally reciprocate the tip of an instrument to fracture the cataract after which it can be aspirated.
A further type of instrument is disclosed in U.S. Pat. No. 4,908,015 issued to Anis on Mar. 13, 1990. This patent describes an instrument which rotates a solid member having blades extending from it to grind the lens.
These tissue removal techniques have several disadvantages, such as: (1) they risk tearing the capsular wall with the reciprocating ultrasonic vibration tools or with the rotating blades; (2) under some circumstances, they require large incisions in or removal of parts of the capsular wall; and (3) they may require the use of several different instruments.
Still another type of prior art technique for removing cataracts is disclosed in U.S. Pat. No. 3,996,935 to Banko issued Dec. 14, 1976. This type of instrument shows cooperating jaw-like members, one of which rotates inside the other to break up the lens by shearing sections of it. It aspirates fragments through the instrument. This type of instrument has a disadvantage in that it can break the capsular wall and is relatively complex. Part of the disadvantage comes from the teaching that it may be rotated manually or mechanical without a corresponding teaching of the rate of rotation required for efficient use.
Still another prior art instrument includes a small rotary magnetic cutter that is injected through the capsular wall and a means for applying magnetic fields that control the magnetic cutter in position. The small magnetic cutter is rotated as it moves from position to position in the capsular bag and to abrade or cut the lens that is to be removed.
This instrument has several disadvantages, such as: (1) it is relatively complicated and expensive because of the need to remotely control the small cutter; and (2) does not incorporate any mechanism for aspirating the lens particles as they are abraded from the lens.
In still another prior art device disclosed in U.S. Pat. No. 4,002,169, small retractable wires are rotated in a range of 5 rpm to 16,000 rpm. There is no teaching of selecting the speed for surface discrimination and the device relies on blunt surfaces to avoid damage to the capsular wall instead. This device has the disadvantages of: (1) providing a relatively slow cutting velocity range with blades not shaped for cavitation or turbulance; (2) not providing a range of velocities sufficient to form small particles that can be aspirated through a small hole; and (3) not providing for aspiration during fragmenting, thus blocking visibility with particles.